Like many companies, Light Crafts releases its flagship application -- the RAW photo converter LightZone -- for Windows, Mac OS X, and Linux. But although the Windows and OS X versions of LightZone cost hundreds of dollars, the Linux version is absolutely free. It is a lucky break, too, because LightZone is a powerful tool that bests many of its expensive competitors on both quality and ease of use.

The LightZone Web site focuses on the commercial products; to get the Linux build you must visit a separate page maintained by Light Crafts' Anton Kast. Kast is the company's chief architect, was the first employee, and is a die-hard Fedora Linux user. LightZone is written in Java and was designed from day one to be cross-platform, so when Kast started work on it, he did so on his platform of choice, all the while making sure that the Linux builds worked just as well as those for proprietary operating systems.

The current Linux bundle (version 2.1) weighs in at a hefty 25MB, thanks to the included Java runtime. (The company used to provide both bundled-runtime and standalone versions of the app, but found that the standalone versions were causing more problems than they solved.) When the download is complete, you can untar the file to any location on your system and launch it with ./LightZone.

Here is where it gets interesting. If you have used a RAW photo app before (such as Bibble or Raw Therapee, for instance), then you probably expect to see a glut of slider controls filling up every spare inch of vertical screen real estate, broken up by a few check boxes and spin buttons. LightZone doesn't stoop that low. Instead, it gives you a sparse toolbar of adjustment functions. You can stack as many of them onto the image as you want, rearrange them, disable them, even remove them. All adjustments are reversible, and nothing touches the original file.

Most RAW converters give you one control for each possible image feature -- white balance, exposure compensation, and so on. In contrast, LightZone treats each adjustment you make as a separate entity -- somewhat like an adjustment layer in Adobe Photoshop lingo.

For example, to adjust the color balance, you click on the color balance tool, and it is stacked on top of your previous adjustments. Then you can adjust the color to your liking, and if you wish, add a second color balance action on top of it. Change your mind about the first one? Just click the X button and ditch it; the rest of the adjustments are retained.

Editing in LightZone. Click to enlarge

With this approach, you can mask off different portions of the image for each adjustment, or you may find it easier to think about the necessary color correction in two steps. In a lot of ways, that is a more natural approach to touching up photos: the actions that you take are the primitives, rather than the esoteric mathematical qualities of the conversion. It is easier to get the image you want by making separate adjustments to distinct problem areas than by trying to find one setting that corrects everything.

Get in the zone

LightZone takes its name from the zone system popularized by photographer and writer Ansel Adams. The original zone system is a set of methods for measuring the dynamic range in a real-world scene and reproducing it in print by adjusting exposure and development. The zones are the 10 steps from absolute black to absolute white that are discernible to the human eye. The methods involve consciously re-mapping the brightness of a scene (from shadows to highlights) so that all 10 zones are covered; this is what gives Adams' photos their wide tonal range without making them look artificially contrasty.

LightZone mimics the zone system with its ZoneMapper tool. A ZoneMapper is a flexible control that plots the luminance of an image against an Adams-style zone system chart.

As you mouse over the chart, LightZone highlights the matching-brightness portions of the image in its preview box. You can grab any point on the chart and slide it up or down to adjust the image's brightness, you can add multiple control points to make finer adjustments, and you can add but not move control points to keep certain brightness levels fixed. As with all tools in LightZone, you can add multiple ZoneMappers to your image in any order.

It is a very intuitive way to adjust a photo; the visual feedback is instantaneous and the control chart interface is far superior to incrementing and decrementing a text-box of decimal values.

The new release of LightZone adds another distinctive tool called ToneMapper, which is a generalization of the contrast mask technique available in many raster image editors. For the uninitiated, a contrast mask is a blurred, black/white-inverted copy of the image that is blended with the original. The blurred, inverted blend does an excellent job of increasing image sharpness and contrast on the small scale without affecting the overall image contrast.

ToneMapper is nowhere near as interesting as ZoneMapper, but it is a nice touch. In most other image editors you can only use a contrast mask if you create one manually with multiple image layers.

LightZone's last big selling point is that it is completely non-destructive. No operations ever alter the original RAW image file. You can export your corrected image to JPEG or TIFF format, but "saving" the file constitutes something different.

What LightZone saves is a .lzn file, by default using the same file name as the original before the .lzn suffix. The .lzn file is XML; it contains the name and location of the original RAW image and a copy of all of the operations you performed on it in LightZone.

In addition to the safety of this technique and small size of the file it generates, Kast believes that the human- and machine-readability of XML make the format useful for automating batch jobs. He described one such use case from his own experience, in which he faced the task of cropping and correcting a large number of photos destined for an eBay auction. But since they were all the same size, he only needed to fix one of them in LightZone. He then wrote a bash script that duplicated the .lzn file for every other file, changing the XML reference in each duplicate to point to one of the other originals -- a far, far faster solution that scripting the same behavior with macros in Photoshop.

Step three: profit!

I give high marks to LightZone across the board. Its interface is intuitive and superior in many respects to the cluttered slider-shelf of most RAW photo tools. Furthermore, it is considerably faster than many of the other options on Linux. The selection and editing tools are excellent. Since it uses dcraw (like most other RAW converters), it has fantastic camera support, and it integrates well with Linux color management and printing systems.

But isn't it just plain weird to offer a product like this for free on Linux, and for $250 on Windows and OS X? Kast concedes that it is an odd choice from a business perspective -- odd enough that he must maintain a FAQ list on the LightZone for Linux page reassuring visitors that the app is neither crippled, pirated, nor a hoax.

In spite of that confusion, he says that the company gets more from its Linux customers than it loses in hypothetical sales. Kast ensures that the Linux version works because it is his platform of choice. The rest of the company required "absolutely no persuasion" on his idea of releasing the it free of charge. The company felt that Linux licenses would be a fraction of Windows and Mac sales, and not worth the marketing expense.

But as a free download, LightZone attracts as many customers as Windows does at its current price point. And those Linux users are dedicated, assisting with bug reports, translations, and valuable feedback. "The Linux version gets us so much user connection and goodwill. A company can have a whole different kind of conversation with no-charge Linux users than it can have with supported Mac/Win users."

Kast and the other programmers develop for all three platforms concurrently. When there is platform-specific work, such as color management, they tackle the Windows version first, but whenever possible release all three simultaneously.

Linux users can participate in the official Light Crafts support forum to ask questions, but Kast also suggests that they subscribe to the LightZone mailing list, which is more technically oriented and makes for faster feedback from the developers.

LightZone 2.1 was released last month for Windows, Mac OS X, and Linux. The Windows and OS X versions are available in a Basic edition for $150 and a Full version for $250. The Linux version is functionally equivalent to the Full version, and is free.